In recent years, electric vehicles each configured to travel using a vehicle-mounted storage battery such as an EV (electric vehicle), PHEV (plug-in hybrid electric vehicle) or HEV (hybrid electric vehicle) are becoming popular. There are vehicle-mounted power supply apparatuses that charge a storage battery mounted on these electric vehicles from power supplies outside the vehicles and use electric energy stored in the storage battery outside the vehicles.
There are conventional vehicle-mounted power supply apparatuses that directly output DC electric energy stored in a vehicle-mounted storage battery to the outside of the vehicle. The DC electric energy outputted from the vehicle-mounted power supply apparatus is converted to AC electric energy by a stationary power generating apparatus installed outside the vehicle and supplied to a house or the like (e.g., PTL 1).
There are also vehicle-mounted power supply apparatuses that convert DC electric energy stored in a vehicle-mounted storage battery to DC electric energy at a voltage varying depending on power of the storage battery by a DC/DC converter and output the DC electric energy to the outside of the vehicle. The DC electric energy outputted from the vehicle-mounted power supply apparatus is used to charge another vehicle-mounted storage battery (e.g., PTL 2).
DC/DC converters can also supply a predetermined low DC voltage to drive devices operating on a low voltage such as air conditioners.